Cog Dielectric Composition For Use With Nickel Electrodes

ABSTRACT

Multilayer ceramic chip capacitors which satisfy COG requirements and which are compatible with reducing atmosphere sintering conditions so that non-noble metals such as nickel and nickel alloys thereof may be used for internal and external electrodes are made in accordance with the invention. The capacitors exhibit desirable dielectric properties (high capacitance, low dissipation factor, high insulation resistance), excellent performance on highly accelerated life testing, and very good resistance to dielectric breakdown. The dielectric layers comprise a strontium zirconate matrix doped with other metal oxides such as TiO 2 , MgO, B 2 O 3 , CaO, Al 2 O 3 , SiO 2 , and SrO in various combinations.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a zirconate titanate based dielectriccomposition, and more particularly to astrontium-zirconate-titanate-based dielectric composition that can beused to form multilayer ceramic chip capacitors having internal basemetal electrodes formed of nickel or nickel alloys.

2. Description of Related Art

Multilayer ceramic chip capacitors have been widely utilized asminiature-sized, high capacitance and high reliability electroniccomponents. In accordance with increasing demands for high-performanceelectronic equipment, multilayer ceramic chip capacitors also haveencountered marketplace demand for smaller size, higher capacitance,lower cost, and higher reliability.

Multilayer ceramic chip capacitors generally are fabricated by formingalternating layers of an internal electrode forming paste and adielectric layer-forming paste. Such layers are typically formed bysheeting, printing, or similar techniques, followed by concurrentfiring.

Generally, the internal electrodes have been formed of conductors suchas palladium, gold, silver or alloys of the foregoing. Althoughpalladium, gold and silver are expensive, they can be partially replacedby the use of relatively inexpensive base metals such as nickel and itsalloys. A “base metal” is any metal other than gold, silver, palladium,and platinum. Base metal internal electrodes can become oxidized iffired in ambient air, so the dielectric layers and internal electrodelayers must be co-fired in a reducing atmosphere. Firing in a reducingatmosphere, however, causes the dielectric layers to be reduced, whichdecreases resistivity. Multilayer ceramic chip capacitors usingnon-reducible dielectric materials have been proposed, however, suchdevices typically have a shorter life of insulation resistance (IR) andlow reliability.

The Electronic Industry Association (EIA) prescribes a standard for thetemperature coefficient of capacitance (TCC) known as the COGcharacteristic. The COG characteristic requires that the change ofcapacitance be no greater than 30 ppm per degree centigrade (±30 ppm/°C.) over the temperature range −55° C. to +125° C. COG components do notexhibit capacitance aging.

SUMMARY OF THE INVENTION

The present invention provides a dielectric composition that can be usedto make ceramic multilayer capacitors compatible with internalelectrodes containing base metals such as nickel or nickel alloys.Capacitors may be formed from the dielectric composition of the presentinvention to exhibit a stable dielectric constant with a smalldielectric loss and excellent reliability under highly accelerated lifetesting conditions.

The dielectric composition of the present invention comprises a uniformdense microstructure of grains having an average diameter of about 0.5to about 3 microns. A uniform and dense grain microstructure is criticalin achieving high reliability multilayer capacitors having dielectriclayers thinner than 5 microns.

In one embodiment, the dielectric composition of the present inventioncomprises, prior to firing, a blend of the oxides of strontium,titanium, and zirconium. Oxides to aid in sintering such as MgO, B₂O₃,and MgO—CaO—SrO—Al₂O₃—SiO₂ may be added. Another embodiment of thepresent invention is an electronic device comprising a multilayer chipcomprising a dielectric layer comprising a strontium-zirconate-titanatemix and a magnesium oxide-boron oxide mix. Yet another embodiment of thepresent invention is an electronic device comprising a multilayer chipcomprising a dielectric layer comprising a strontium zirconate titanatemix and a MgO—CaO—SrO—Al₂O₃—SiO₂ mix.

In another embodiment, the present invention provides a method offorming an electronic component comprising applying particles of adielectric material to a substrate and firing the substrate at atemperature sufficient to sinter the dielectric material, wherein thedielectric material comprises, prior to firing, a blend (in weightpercent) of the ingredients in Table 1. It is to be understood that eachnumerical value herein (percentage, temperature, etc) is presumed to bepreceded by “about.”

TABLE 1 Oxide formulations of dielectric compositions. SrO ZrO₂ TiO₂B₂O₃ MgO wt % 41.5-48.5 47-55 1-2 0.05-3 0.05-1.5

Another route is to begin with strontium carbonate, titanium dioxide,and zirconium oxide. The composition can also be made by firing a blendof one or more pre-reacted oxides such as SrTiO₃ or SrZrO₃. In thisregard, the formulation of Table 2 will result in approximately the samedielectric material as that made by the formulation of Table 1.

TABLE 2 Alternate formulation for dielectric material. SrCO₃ TiO₂ ZrO₂MgO B₂O₃ wt % 52.0-56.0 1.0-2.0 41.0-45.0 0.05-1.5 0.05-3.0

In another embodiment, the dielectric material comprises, prior tofiring, a blend (in weight percent) of the ingredients in Table 3.

TABLE 3 Alternate formulation of dielectric compositions. SrO ZrO₂ TiO₂MgO CaO Al₂O₃ SiO₂ wt 44.2-45.6 50.2-51.8 1.5-1.6 0.1-0.4 0-0.3 0.3-1.20.5-2.2 %

Another embodiment of the present invention is a multilayer ceramic chipcapacitor comprising alternately stacked layers of a dielectric materialand an internal electrode material comprising a transition metal otherthan Ag, Au, Pd, or Pt, wherein the dielectric material comprises asintered blend of any of the formulations of Tables 1, 2, or 3. Yetanother embodiment is a lead-free and cadmium-free dielectric pastecomprising a solids portion wherein the solids portion comprises a glasscomponent, wherein the glass component comprises, prior to firing, theingredients of Table 1, Table 2, or Table 3.

The foregoing and other features of the invention are hereinafter morefully described and particularly pointed out in the claims, thefollowing description setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principles of the present inventionmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a cross-sectional view of a multilayer ceramic chip capacitoraccording to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Multilayer chip capacitors are fabricated by alternately stackingdielectric layers and internal electrodes to form green chips. Theinternal electrodes of interest herein are comprised of base metalsincluding nickel or nickel alloys. The dielectric composition that formsthe dielectric layers is produced by wet milling the components of thedielectric with an organic vehicle system. The dielectric composition isdeposited on a carrier film, such as polyester or polypropylene, or abelt, such as stainless steel, paper, or a substrate such as alumina orglass, coating the film, and forming sheets, which are alternatelystacked with electrodes to form the green chips.

After the green chips are formed, the organic vehicle is removed byheating to a temperature less than about 350° C. in an air atmosphere.Once the vehicle is removed, the green chips are then fired in areducing atmosphere of wet nitrogen and hydrogen having an oxygenpartial pressure of about 10⁻¹² to about 10⁻⁸ atm, at a temperature ofabout 1200° C. to about 1350° C. Various heating profiles may be usedboth for removing the binder and for firing the chip.

The configuration of multilayer ceramic capacitors is well known in theart. With reference to FIG. 1, an exemplary structure of a multilayerceramic chip capacitor 1 is shown. External electrodes 4 of thecapacitor 1 are disposed on side surfaces of the capacitor chip 1 and inelectrical connection with internal electrode layers 3. The capacitorchip 1 has a plurality of alternately stacked dielectric layers 2. Theshape of the capacitor chip 1 is not critical although it is oftenrectangular shaped. Also, the size is not critical and the chip may haveappropriate dimensions in accordance with a particular application,typically in the range of 1.0 to 5.6 mm×0.5 to 5.0 mm×0.5 to 1.9 mm. Theinternal electrode layers 3 are stacked such that at opposite ends theyare alternately exposed at opposite side surfaces of the chip 1. Thatis, the internal electrode layers 3 of one group are exposed at one sidesurface of the chip 1 and the internal electrode layers 3 of anothergroup are exposed at the opposite side surface of the chip 1. Oneexternal electrode 4 is applied to one side surface of the capacitorchip 1 in electrical contact with the internal electrode layers 3 of theone group, and the other external electrode 4 is applied to the oppositeside surface of the chip 1 in electrical contact with the internalelectrode layers 3 of the other group.

The dielectric layers are formed of a dielectric material formed bysintering a blend including oxides of strontium, titanium and zirconium,as in Tables 1, 2, or 3. A sintering aid including B₂O₃, MgO orMgO—CaO—Al₂O₃—SiO₂—SrO may be useful.

Another route is to begin with strontium titanate and strontiumzirconate, as in Tables 4 or 5. It should be evident to those who arefamiliar with the art that the above mentioned oxides in their hydroxideor other forms such as carbonates, acetates, nitrates, andorganometallic compounds such as metal formates, oxalates, etc., havethe same effect, so long as the desired metal ion is provided in thedesired quantity.

TABLE 4 Alternate formulation of dielectric compositions. SrTiO₃ SrZrO₃B₂O₃ MgO wt % 1-7 89-99 0.05-3 0.05-1.5

TABLE 5 Alternate formulations for dielectric compositions. wt % SrCO₃SrZrO₃ SrTiO₃ SrO ZrO₂ TiO₂ MgO CaO Al₂O₃ SiO₂ A 50-58   0-0.5 40-460.5-3   0.05-1 0-1   0.05-2 0.05-3   B 90-98 2-5 0-1 0.05-2 0-1.5 0.05-20.05-3.5 C 92.5-95.4 3.5-3.6   0.1-0.4 0-0.3   0.3-1.2   0-0.3 D41.5-48.5 47-55 0.5-2.5 0.05-1 0-0.5   0.05-2.5 0.05-3.5

Other compounds may be present in the dielectric material provided thatthe other compound does not adversely affect dielectric properties. Suchcompounds are usually found in the raw materials as impurities.

The dielectric compositions herein possess fine crystal grains thattypically have a mean size of about 0.5 to about 3 microns, with a grainsize of less than about 0.7 micron being preferred.

Each dielectric layer has a thickness of up to about 50 microns.Preferably, the thickness of each dielectric layer is from about 0.5microns to about 50 microns. More preferably, the thickness of eachdielectric layer is from about 2 microns to about 10 microns. Thecompositions herein may be employed to make multilayer ceramic chipcapacitors having thin dielectric layers to ensure minimal degradationof capacitance over the service life. The number of dielectric layersstacked in a chip capacitor is generally from about 2 to about 800, andpreferably from about 3 to about 400.

The multilayer ceramic chip capacitor of the invention generally isfabricated by forming a green chip by conventional printing and sheetingmethods using pastes, and firing the green chip. After firing, the chipis tumbled dry in a medium such as alumina or silica to round offcorners. Next, a conductive paste, containing, for example, copper isthen applied to both ends to connect the exposed inner electrodestogether to make terminations. The chip is then termination fired atabout 800° C. in a nitrogen atmosphere to sinter the conductor (e.g.,copper) into a solid conduction pad at both ends, to form a multilayercapacitor. The terminations are external electrodes 4 as shown in FIG.1.

Dielectric Pastes. A paste for forming the dielectric layers can beobtained by mixing an organic vehicle with a raw dielectric material, asdisclosed herein. Also useful are precursor compounds that convert tosuch oxides and composite oxides upon firing, as stated hereinabove. Thedielectric material is obtained by selecting compounds containing theseoxides, or precursors of these oxides, and mixing them in theappropriate proportions. The proportion of such compounds in the rawdielectric material is determined such that after firing, the desireddielectric layer composition may be obtained. The raw dielectricmaterial is generally used in powder form having a mean particle size ofabout 0.1 to about 3 microns, and more preferably about 1 micron orless.

Organic Vehicle. The organic vehicle is a binder in an organic solventor a binder in water. The choice of binder used herein is not critical;conventional binders such as ethyl cellulose, polyvinyl butanol, ethylcellulose, and hydroxypropyl cellulose, and combinations thereof areappropriate together with a solvent. The organic solvent is also notcritical and may be selected in accordance with a particular applicationmethod (i.e., printing or sheeting), from conventional organic solventssuch as butyl carbitol, acetone, toluene, ethanol, diethylene glycolbutyl ether; 2,2,4-trimethyl pentanediol monoisobutyrate (Texanol®);alpha-terpineol; beta-terpineol; gamma terpineol; tridecyl alcohol;diethylene glycol ethyl ether (Carbitol®), diethylene glycol butyl ether(Butyl Carbitol®) and propylene glycol; and blends thereof, Productssold under the Texanol® trademark are available from Eastman ChemicalCompany, Kingsport, Tenn.; those sold under the Dowanol® and Carbitol®trademarks are available from Dow Chemical Co., Midland, Mich.

Alternatively, the binder could be selected from polyvinyl alcohol (PVA)or polyvinyl acetate (PVAC) in combination with water. It should benoted that PVA and PVAC are generally not compatible with boroncontaining ceramic dielectric powders. An aqueous slurry including aboron containing glass together with PVA and/or PVAC tends to suffersevere gelation. Therefore, ceramic dielectric powders that do notcontain boron, as disclosed in this invention, are of particularimportance for water based slurry processing.

No particular limit is imposed on the organic vehicle content of therespective pastes (dielectric or electrode pastes). Often the pastecontains about 1 to 5 wt % of the binder and about 10 to 50 wt % of theorganic solvent, with the balance being either the metal component (foran electrode) or a dielectric component (for a dielectric layer). Ifdesired, the respective pastes may contain up to about 10 wt % of otheradditives such as dispersants, plasticizers, dielectric compounds, andinsulating compounds.

Internal Electrode. A paste for forming internal electrode layers isobtained by mixing an electro-conductive material with an organicvehicle. The conductive material used herein includes conductors such asconductive metals and alloys as mentioned herein and various compoundswhich convert into such conductors upon firing, for example, oxides,organometallic compounds and resinates. An example of a suitable nickelpaste is EL51-012 nickel paste from Ferro Corporation.

With reference to FIG. 1, the conductor that forms the internalelectrode layers 3 is not critical, although a base metal preferably isused since the dielectric material of the dielectric layers 2 hasanti-reducing properties. Typical base metals include nickel and itsalloys. Preferred nickel alloys contain at least one other metalselected from Mn, Cr, Co, Cu, and Al. Alloys containing at least about95 wt % of nickel are preferred. It is to be noted that nickel andnickel alloys may contain up to about 0.1 wt % of phosphorous and othertrace components (i.e., impurities). The thickness of the internalelectrode layers may be controlled to suit a particular application, butthe layers are typically up to about 5 microns thick. Preferably, aninternal electrode layer has a thickness of about 0.5 to about 5 micronsand more preferably about 1 to about 5 microns.

External Electrode. The conductor that forms the external electrodes 4is not critical, although inexpensive metals such as copper, nickel, andalloys of either or both, optionally containing Mn, Cr, Co, or Al, arepreferred. The thickness of the external electrode layers may becontrolled to suit a particular application, but the layers aretypically up about 10 to about 50 microns thick, preferably about 20 toabout 40 microns thick. Paste for forming external electrodes isprepared by the same method as for the internal electrodes.

A green chip then may be prepared from the dielectric layer-formingpaste and the internal electrode layer-forming paste. In the case of aprinting method, a green chip is prepared by alternately printing thepastes onto a substrate of a polyester film, (e.g., polyethyleneterephthalate (PET)), in laminar form, cutting the laminar stack to apredetermined shape and separating it from the substrate. Also useful isa sheeting method wherein a green chip is prepared by forming greensheets from the dielectric layer-forming paste, printing the internalelectrode layer-forming paste on the respective green sheets, andstacking the printed green sheets. After the organic vehicle is removedfrom the green chip, it is fired. The organic vehicle may be removedunder conventional conditions, by heating at a rate of 0.01° C. to 20°C./hour, more preferably about 0.03-0.1° C./hour, with a holdtemperature of about 150° C. to about 350° C., preferably about 200° C.to about 300° C., more preferably about 250° C., and a hold time ofabout 30-700 minutes, preferably about 200-300 minutes in an airatmosphere.

Firing. The green chip is then fired in an atmosphere, which isdetermined according to the type of conductor in the internal electrodelayer-forming paste. Where the internal electrode layers are formed of abase metal conductor such as nickel and nickel alloys, the firingatmosphere may have an oxygen partial pressure of about 10⁻¹² to about10⁻⁸ atm. Sintering at a partial pressure lower than about 10⁻¹² atmshould be avoided, since at such low pressures the conductor can beabnormally sintered and may become disconnected from the dielectriclayers. At oxygen partial pressures above about 10⁻⁸ atm, the internalelectrode layers may be oxidized. Oxygen partial pressures of about10⁻¹¹ to about 10⁻⁹ atm are most preferred.

For firing, the temperature is raised from room temperature to a peaktemperature of from about 1150° C. to about 1350° C., more preferablyfrom about 1250° C. to about 1350° C. The temperature is held for abouttwo hours to enhance densification. Lower hold temperatures provideinsufficient densification whereas higher hold temperatures can lead tovery large grains. The firing is preferably conducted in a reducingatmosphere. An exemplary firing atmosphere includes wet N₂, or ahumidified mixture of N₂ and H₂ gases. The sintering ramp rate is about50° C. to about 500° C./hour, preferably about 200° C. to 300° C./hour;hold temperature of about 1200° C. to about 1350° C., preferably about1250° C. to about 1350° C., more preferably about 1275° C. to about1325° C. The hold time is about 0.5 to about 8 hours, preferably about 1to 3 hours, and the cooling rate is about 50° C. to 500° C./hour,preferably about 200° C. to 300° C./hour.

The organic vehicle removal and firing may be carried out eithercontinuously or separately. If continuously, the process includesorganic vehicle removal, changing the atmosphere without cooling,heating to the firing temperature, holding at the firing temperature fora specified time and cooling afterwards. If separately, after organicvehicle removal and cool down, the temperature of the chip is raised tothe sintering temperature and the atmosphere then is changed to areducing atmosphere.

The resulting chip may be polished at end faces by barrel tumblingand/or sand blasting, for example, before the external electrode-formingpaste is printed or transferred and fired to form external electrodes(terminations). Firing of the external electrode-forming paste may becarried out in a dry nitrogen atmosphere (about 10⁻⁶ atm oxygen partialpressure), at about 600° C. to 800° C., for about 10 minutes to about 1hour.

If necessary, pads are formed on the external electrodes by plating orother methods known in the art. The multilayer ceramic chip capacitorsof the invention can be mounted on printed circuit boards, for example,by soldering.

EXAMPLES

The following examples are provided to illustrate preferred aspects ofthe invention and are not intended to limit the scope of the invention.

Overview. Multilayer ceramic capacitors with pure nickel electrodes, 10active layers, with each layer being 5 to 10 microns thick were preparedand sintered in a reducing atmosphere (pO₂ of 10⁻¹¹ to 10⁻⁸ atm) at1275° C. to 1350° C. Physical and electrical measurements were carriedout. The fired chips exhibited a dielectric permittivity over 30,DF<0.1% at 1 MHz, TCC of less than ±30 ppm/° C. from −55° C. to +125°C., IR>10¹³ ohms at 25° C., IR>10 ohms at 125° C. The dielectricbreakdown voltage exceeds 140 V/micron. Reliability test was conductedby subjecting chips at 140° C. with 300V DC voltage applied. No failurewas observed after 115 hours.

Example 1

A dielectric composition identified as Precursor 1 was formed by mixing,blending, and/or milling in water appropriate amounts of the oxides asshown in Table 6. The powders were mixed at high shear (about 5000/min)with 1% Darvan®C, a polymeric deflocculant available from RT VanderbiltCo., Inc., Norwalk, Conn. The mixed powders were bead milled to aparticle D₅₀ of about 0.65 micron using 0.5 mm YTZ (yttria stabilizedzirconia). The powders are calcined at 1200° C. for 5 hours. Thecalcined powders are then pulverized by conventional means to affordPrecursor 1.

TABLE 6 Formulation of Precursor 1 prior to calcination. SrCO₃ ZrO₂ TiO₂wt % 54.901 43.761 1.337

Alternately, the composition of Precursor 1, after calcination, can berepresented by the following expression: SrZr_(o.955)Ti_(0.045)O₃. ToPrecursor 1 was added 2MgO3 B₂O₃ (as a combination of Mg(OH)₂ andH₃BO₃), as a sintering flux, in accordance with the formulation in Table7. Again, the blended powders are mixed at high shear (about 5000/min),bead milled to a particle D₅₀ of about 0.40 micron using 0.5 mm YTZ,dried and pulverized by conventional means to afford the dielectricpowder of Example 1.

TABLE 7 Formulation of Example 1 dielectric powder prior to firing.Precursor 1 Mg(OH)₂ H₃BO₃ wt % 98.377 0.787 0.836

The powder of Example 1 contains the combination of simple oxides as setforth in Table 8 and has a formula that may be expressed alternately as:98.979 wt % of SrZr_(0.955)Ti_(0.045)O₃+0.547 wt % of MgO+0.474 wt %B₂O₃.

TABLE 8 Oxide ingredients of Example 1 dielectric powder. SrO ZrO₂ TiO₂MgO B₂O₃ wt % 45.606 51.791 1.583 0.547 0.474 Mol % 48.869 46.669 2.1991.507 0.756

The final powders had an average particle size of 0.3 to 1 micron. Onehundred grams of the above powders was then added to 28.8 grams of anorganic vehicle comprising polyvinyl butanol, toluene, and ethanol, andwet milled for 24 hours to prepare a slurry for tape casting. The wetslurry was coated on a polyester film to form dielectric green tapes.The thickness of the dielectric green tapes was from about 5 to about 15microns depending on the specific testing to be performed on them.Nickel electrodes were printed onto the dried green dielectric tape byconventional screen-printing methods using a conventional nickel paste.A total of 10 sheets were stacked and bonded under a pressure of 5100psi and a temperature of 130° F. (54° C.) to form a green chip. Afterdicing to a suitable dimension so that, after sintering and shrinkage,(which is typically from 15% to 20% in both X and Y directions), thechip dimension is about 0.12″(L)×0.06″(W) (EIA1206 size) or0.08″(L)×0.05″(W) (EIA0805 size), the green chip was heated to removethe organic vehicle accordance with the burn-out cycle of Table 9.

TABLE 9 Binder removal conditions. Stage Temp (° C.) Duration (min)Atmosphere Ramp from room temp 265 1200 Air Soak 265  240 Air Cool toroom temp 25 to reach 25° C. Air

For all examples, chips first had their binder removed at a temperatureof about 265° C. (Table 9) and then were sintered at a temperature from1250° C. to 1350° C. in a gas mixture of N₂/H₂/H₂O at a pO₂ from 10⁻¹¹to 10⁻⁸ atm. The gas mixture was achieved by humidifying the N₂/H₂ gasesthrough a wetter with a water temperature of 35° C. The chip thusobtained was corner rounded by tumbling. An external electrode formingcopper paste available as TM50-081 from Ferro Corporation of Cleveland,Ohio was applied to the end faces and fired in a dry nitrogen atmosphereat 775° C. for about 70 minutes to form external electrodes. Themultilayer capacitor thus processed had dimensions of about 3.2 mm×1.6mm (EIA 1206 size) or about 2.1 mm×1.3 mm (EIA0805 size) with variablethickness. The dielectric layers were 6 to 15 microns thick, and theinternal nickel electrode layers were about 1.5 microns thick.

Multilayer chip capacitors were made from the powders of Example 1 andtested. Firing conditions as well as electrical properties aresummarized in Table 10. All examples (1a to 1g) in Table 10 were firedat the indicated temperature for 2 hours.

TABLE 10 Firing conditions and electrical properties for MLCCs ofExample 1. Example 1a 1b 1c 1d 1e 1f 1g Sintering Temp (° C.) 1275   1275    1300    1300    1325    1325    1325    pO₂ (atm)  10⁻¹⁰  10⁻¹¹ 10⁻¹⁰  10⁻¹¹ 10⁻⁸ 10⁻⁹  10⁻¹⁰ Dielectric Thickness (microns)  5.0  4.7 5.1  5.0  5.2  5.0  5.4 Capacitance (pF) 386.5  363.2  412.2  391.8 422.6  418.5  406.5  DF (%)   0.019   0.003   0.007   0.008   0.023  0.013   0.023 Dielectric Constant 30.0 27.9 34.8 32.5 38.4 36.3 29.5TCC (ppm/° C.)  25° C. −12.4  −12.2  −6.7 −12.2  −11.6  −8.8 −3.8  85°C. −2.2 −3.8 −0.3 −3.4 −7.8 −1.0  3.3 125° C. −1.8 −2.6  1.0 −2.2 −1.8 0.0  7.0 IR (10¹² OHM)  25° C. 900   760   270   440   390   660  420   125° C. 47.0  8.6 13.0  5.8  6.3  7.5  9.8 Breakdown Voltage (V)1060    945   977   880   1005    811   714  

Example 2

To precursor 1 was added a mixture of Mg(OH)₂, CaCO₃, Al₂O₃ and SiO₂according to Table 11, as a sintering aid (effectively resulting inMgO—CaO—Al₂O₃—SiO₂ after firing). The powder was processed according toExample 1.

TABLE 11 Formulation of Example 2 dielectric prior to firing Precursor 1Mg(OH)₂ CaCO₃ Al₂O₃ SiO₂ wt % 97.812 0.257 0.257 0.579 1.096The powder of Example 2 has a formula that may be expressed alternatelyas: 98.003 wt % of SrZr_(0.955)Ti_(0.045)O₃+0.178 wt % of MgO+0.144 wt %of CaO+0.579 wt % of Al₂O₃+1.096 wt % of SiO₂. When expressed as simpleoxides, the powder of Example 2 has the formulations of Table 12.

TABLE 12 Oxide ingredients of Example 2 dielectric powder. SrO ZrO₂ TiO₂MgO CaO Al₂O₃ SiO₂ Wt % 45.156 51.281 1.567 0.178 0.144 0.579 1.096 Mol% 48.288 46.115 2.173 0.489 0.285 0.629 2.021The final powder of Example 2 was processed according to the proceduresof Example 1 to fabricate MLCC chips for electrical testing. Firingconditions as well as electrical properties are summarized in Table 13.Examples 2a to 2d in Table 13 were fired at the indicated temperaturefor 2 hours.

TABLE 13 Firing conditions and electrical properties for MLCCs ofExample 2. Example 2a 2b 2c 2d Sintering Temp (° C.) 1300 1300 1325 1350pO₂ (atm)  10⁻¹⁰  10⁻¹¹  10⁻¹⁰  10⁻¹⁰ Dielectric Thickness  12.3  11.3 11.0  10.9 (microns) Capacitance (pF)  152.7  158.2  164.7  166.5 DF(%)   0.005   0.070   0.010   0.007 Dielectric Constant  31.2  32.3 31.4  31.5 TCC (ppm/° C.)  25° C.  −4.8  −3.8   0.5   0.2  85° C.   4.5  4.0   7.3   7.2 125° C.   4.5   5.0   8.0   7.6 IR (10¹² OHM)  25° C. 100.0  31.0   5.0  34.0 125° C.   6.5   5.0   2.1   3.0 BreakdownVoltage (V) 1726  909 1565 1562

Examples 3-14

To Precursor 1 was added various amounts of a mixtures including any orall of MgO, CaO, Al₂O₃, SiO₂, and/or SrO as a sintering aid inaccordance with the formulations of Examples 3-14 in Table 14. Becausethe sintering aid in Examples 12, 13 and 14 also contain SrO, the totalSrO in those examples comes both from Precursor 1 and from the sinteringaid. The total weight of Precursor 1 is the sum of the first threecolumns (SrO, ZrO₂ and TiO₂) for Examples 3 to 14. For the purpose ofeasy comparison, the composition and MLCC electrical properties ofExample 2 are also included in Tables 14 and 15.

TABLE 14 Oxide ingredients of Examples 2-14 powders (in wt %) ExampleSrO ZrO₂ TiO₂ MgO CaO Al₂O₃ SiO₂ SrO from sintering aid 2 45.156 51.2811.567 0.178 0.144 0.579 1.095 0 3 44.236 50.236 1.535 0.355 0.288 1.1582.192 0 4 45.616 51.803 1.583 0.089 0.072 0.290 0.548 0 5 45.160 51.2861.567 0.204 0.108 0.579 1.096 0 6 45.165 51.291 1.567 0.230 0.072 0.5791.096 0 7 45.170 51.296 1.567 0.255 0.036 0.579 1.096 0 8 45.174 51.3071.567 0.281 0.000 0.579 1.096 0 9 45.305 51.450 1.572 0.178 0.144 0.5810.770 0 10 45.355 51.506 1.574 0.178 0.145 0.582 0.661 0 11 45.40551.563 1.575 0.179 0.145 0.582 0.551 0 12 45.173 52.265 1.566 0.1780.108 0.579 1.096 0.036 13 45.190 51.249 1.566 0.177 0.072 0.579 1.0950.072 14 45.221 51.218 1.565 0.177 0.000 0.578 1.095 0.146

The final powders of Examples 3-14 were processed according to theprocedures of Example 1 to fabricate MLCC chips for electrical testing.Firing conditions as well as electrical properties are summarized inTable 14. The MLCCs were fired for two hours each.

TABLE 15 Firing conditions and electrical properties for MLCCs ofExamples 2d-15. Example 2d 3 4 5 6 7 8 Sintering 1350 1325 1350 13501350 1350 1350 Temp (° C.) pO₂ (atm)  10⁻¹⁰  10⁻¹¹  10⁻¹⁰  10⁻¹⁰  10⁻¹⁰ 10⁻¹⁰  10⁻¹⁰ Dielectric  10.9  19.0   3.5  10.3  10.7  11.3  10.8Thickness (microns) Capacitance  166.5  313.1  502.3  180.2  173.2 166.8  172.8 (pF) DF (%)   0.007   0.016   0.012   0.033   0.012  0.006   0.294 Dielectric  31.5  31.0  31.0  31.5  31.7  32.0  30.8Constant TCC (ppm/° C.)  25° C.   0.2  −2.4   2.4  −3.7  −5.6  −6.6 −2.8  85° C.   7.2   7.0  −2.8   4.3   2.6   2.6   1.6 125° C.   7.6  8.4  10.0   7.6   4.7   3.0   2.2 IR (10¹² OHM)  25° C.  34  71  440 85  47  89  17 125° C.   3.0   3.0   1.7   1.8   1.8   1.7   1.2Breakdown 1582 1663  595  765 1259 1419  401 Voltage (V) Example 9 −1011 12 13 14 Sintering 1325 1325 1325 1325 1325 1325 Temp (° C.) pO₂(atm)  10⁻¹⁰  10⁻¹⁰  10⁻¹⁰  10⁻¹⁰  10⁻¹⁰  10⁻¹⁰ Dielectric  13.0  11.4 12.6  13.5  13.1  12.4 Thickness (microns) Capacitance  163.5  169.2 168.9  159.4  163.9  151.5 (pF) DF (%)   0.010   0.011   0.017   0.009  0.015   0.007 Dielectric  35.5  30.6  34.7  37.2  39.8  33.0 ConstantTCC (ppm/° C.)  25° C.  −4.2  −4.0   1.0  −6.2  −2.0  −7.0  85° C.   2.8  3.4   7.0   2.0   6.0   1.2 125° C.   6.3   4.2   7.0   2.8   6.5  2.0 IR (10¹² OHM)  25° C.  140  140  250  57  57  98 125° C.   4.4  2.7   6.4   8.9   2.5   2.1 Breakdown 1892 1605 1735 1533 1036 1578Voltage (V)

The exemplary chips made from the composition of examples 1-14 all havevery high dielectric constants, low DF, small fired grain sizes, andhigh breakdown voltages. The TCC meets the COG standard and the IR at25° C. and 125° C. all exceed EIA specifications.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and illustrative example shown anddescribed herein. Accordingly, various modifications may be made withoutdeparting from the spirit or scope of the general invention concept asdefined by the appended claims and their equivalents.

1. A lead-free and cadmium-free dielectric paste comprising a solidsportion wherein the solids portion comprises, prior to firing: a. about41.5 wt % to about 48.5 wt % SrO, b. about 47 wt % to about 55 wt %ZrO₂, c. about 0.5 wt % to about 2.5 wt % TiO₂, d. about 0.05 wt % toabout 1.5 wt % MgO, and e. about 0.05 wt % to about 3 wt % B₂O₃.
 2. Amethod of forming an electronic component comprising: a. applying thedielectric paste of claim 1 to a substrate and b. firing the substrateat a temperature sufficient to sinter the dielectric material.
 3. Themethod of claim 2 wherein the firing is conducted at a temperature of1200° C.-1350° C.
 4. The method of claim 2 wherein the firing isconducted in an atmosphere having a partial oxygen pressure of about10⁻¹² atm to about 10⁻⁸ atm.
 5. A multilayer ceramic chip capacitorcomprising a fired collection of: a. alternately stacked layers of thedielectric material of claim 1 and b. layers of an internal electrodematerial comprising a transition metal other than Ag, Au, Pd, or Pt. 6.The multilayer ceramic chip capacitor of claim 5 wherein the internalelectrode material comprises nickel.
 7. A method of forming anelectronic component comprising: a. alternately applying layers of i. anoxide-containing dielectric material comprising the paste of claim 1 andii. a metal-containing electrode paste onto iii. a substrate to form alaminar stack, b. firing the substrate at a temperature sufficient tosinter the dielectric material, c. cutting the laminar stack to apredetermined shape, d. separating the cut stack from the substrate, ande. firing the stack to sinter the metal in the electrode and fuse theoxides in the dielectric material, wherein the internal electrode andthe dielectric material each have a layer thickness.
 8. The method ofclaim 7 wherein the layers of dielectric material, after firing, have athickness of about 1 microns to about 50 microns.
 9. The method of claim7 wherein the firing is conducted at a temperature of 1200° C. to about1325° C.
 10. The method of claim 7 wherein the firing is conducted in anatmosphere having a partial oxygen pressure of about 10⁻¹² atm to about10⁻⁸ atm.
 11. The method of claim 7 wherein the metal-containingelectrode paste comprises nickel.
 12. A lead-free and cadmium-freedielectric paste comprising a solids portion wherein the solids portioncomprises, prior to firing: a. about 44.2 wt % to about 45.6 wt % SrO,b. about 50.2 wt % to about 51.8 wt % ZrO₂, c. about 0.1 wt % to about0.4 wt % MgO, d. about 1.5 wt % to about 1.6 wt % TiO₂, e. about 0.3 toabout 1.2 wt % Al₂O₃, f. about 0.5 to about 2.2 wt % SiO₂, and g. up toabout 0.3 wt % CaO.
 13. A method of forming an electronic componentcomprising: a. applying the dielectric paste of claim 12 to a substrateand b. firing the substrate at a temperature sufficient to sinter thedielectric material.
 14. The method of claim 12 wherein the firing isconducted at a temperature of 1200° C.-1350° C., and in an atmospherehaving a partial oxygen pressure of about 10⁻¹² atm to about 10⁻⁸ atm.15. A method of forming an electronic component comprising: a. applyingparticles of a calcined dielectric material to a substrate and b. firingthe substrate at a temperature sufficient to sinter the dielectricmaterial, c. wherein the dielectric material comprises, prior to firing,a composition selected from the group consisting of composition 1,composition 2, composition 3, composition 4, wherein prior to calcining,i. composition 1 comprises
 1. about 1 wt % to about 7 wt % SrTiO₃, 2.about 89 wt % to about 99 wt % SrZrO₃,
 3. about 0.05 wt % to about 3 wt% B₂O₃, and
 4. about 0.05 wt % to about 1.5 wt % MgO, ii. composition 2comprises
 1. about 52 wt % to about 56 wt % SrCO₃,
 2. about 41 wt % toabout 45 wt % ZrO₂,
 3. about 1 wt % to about 2 wt % TiO₂,
 4. about 0.05wt % to about 3 wt % B₂O₃, and
 5. about 0.05 wt % to about 1.5 wt % MgO,iii. composition 3 comprises
 1. about 50 wt % to about 58 wt % SrCO₃, 2.about 40 wt % to about 46 wt % ZrO₂,
 3. about 0.5 wt % to about 3 wt %TiO₂,
 4. about 0.05 to about 1 wt % MgO,
 5. about 0.05 wt % to about 2wt % Al₂O₃,
 6. about 0.05 wt % to about 3 wt % SiO₂,
 7. CaO, providedthe amount does not exceed about 1 wt %, and
 8. SrO, provided the amountdoes not exceed about 0.5 wt %, and iv. composition 4 comprises
 1. about2 wt % to about 5 wt % SrTiO₃,
 2. about 90 wt % to about 98 wt % SrZrO₃,3. about 0.05 to about 2 wt % MgO,
 4. about 0.05 wt % to about 2.5 wt %Al₂O₃,
 5. about 0.05 wt % to about 3.5 wt % SiO₂,
 6. SrO, provided theamount does not exceed about 1 wt %, and
 7. CaO, provided the amountdoes not exceed about 1 wt %.
 16. The method of claim 15 wherein thefiring is conducted at a temperature of 1200° C.-1350° C.
 17. The methodof claim 15 wherein the firing is conducted in an atmosphere having apartial oxygen pressure of about 10⁻¹² atm to about 10⁻⁸ atm.
 18. Themethod of claim 15 wherein the firing is conducted at a temperature of1200° C. to about 1325° C.
 19. The method of claim 15 wherein thedielectric material comprises, prior to firing, composition
 1. 20. Themethod of claim 15 wherein the dielectric material comprises, prior tofiring, composition 3.